The purpose of this prospective study is to determine the relationships of sociodemographic risk factors, biomedical risk factors, and lifestyle behavior risk factors to each other and to low birthweight (LBW) and other adverse pregnancy outcomes, including labor and delivery complications and infant complications. The goal is to reduce the incidence of LBW and adverse pregnancy outcomes by: Aim 1) Developing and testing a biopsychosocial model for predicting LBW and other adverse pregnancy outcomes that will be a significant improvement over current prediction systems; and Aim 2) Determining the extent to which modifiable risk factors are related to LBW and adverse outcomes. Four hypotheses will be tested: 1) The proposed biopsychosocial model will fit the data when tested by LISREL; 2) The proposed biopsychosocial model will be an improvement over current prediction systems; 3) Psychosocial risk will add to the prediction of infant birthweight and other adverse pregnancy outcomes when biomedical risk, sociodemographic risk, and lifestyle behavior risk are controlled; and 4) Lifestyle behavior risk will add to the prediction of infant birthweight and other adverse pregnancy outcomes when biomedical risk, sociodemographic risk, and psychosocial risk are controlled. The sample will include a minimum of 2200 mother-infant pairs. Women will be interviewed at their initial prenatal visit and again between 24- 28 weeks gestation if their initial visit was prior to 20 weeks. Sociodemographic data will be collected at the initial interview. Biomedical risk factors will be collected from chart data at the initial visit and between 24-28 weeks. Women will complete (a) the Psychosocial Assessment Tool, which measures stress, social support, and self-esteem, and (b) a confidential self-report of smoking, alcohol, and drug use at each interview. Outcome data will be collected from hospital records or birth certificates. All data will be collected by trained RAs. Hypothesis 1 will be tested with covariance structure modeling using the LISREL program. Hypothesis 2 will be tested by comparing the model's predictive value and explained variance to existing models. In addition, the model's adjusted odds ratios and clinical utility will be evaluated. Hypotheses 3 and 4 will be tested by hierarchical multiple regression and logistic regression.